Spheres check methods

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robertgillatt
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Post by robertgillatt »

Just a word about replacing Spheres.
The very good technical article on the "Common Problems and Fixes" pages describes the replacement procedure. However [1].I can't see why the 9mm union has to be released - this screws into the aluminium mounting block which is itself restrained when the spheres are being unscrewed. [2]How the hell do you get the spheres moving? I broke my heavy duty chain wrench twice on the first sphere before giving up. I was getting worried about wrenching the back of the car off ! I am off to a friendly workshop tommorrow but any tips to help out the next time would be very welcome.
allmond
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Post by allmond »

Hi
The 9mm union has to be released because it screws into the sphere. Then the sphere itself screws into the mounting. Due to different thread pitches you must undo both parts, otherwise you'll wind the pipe around itself.
Jamie
DLM
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Post by DLM »

When it comes to getting reluctant spheres moving, my opinion is that there is no substitute for:
(a) The right sphere-removing tool - preferably the type of band wrench that Andyspares/Pleiades sell.
(b) Plenty of leverage. Band-wrench handles can normally can be easily fitted with extensions for this purpose. I managed to improvise a very effective one from part of an old exercise cycle frame!
(c) Ensuring that the sphere mounting is effectively locked in position before starting. Wood blocks may help at the front, Stilson wrenches may need to be used on rear cylinders, but I'm not sure what's most appropriate for the anti-sink spheres. Use any passive means available to allow opposing forces to lock the mountings in place.
I find that steady, controlled pressure using an extension bar, rather than hammer blows on the removing tool, are the most effective.
David
mark_l
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Post by mark_l »

For your information:
My friend replaced front and rear spheres on his Xantia '95 1800 before 7 month.
Manufacturer: http://www.lizarte.com/textose/esferas_nuevas.html
In front car dives 4.5 cm, rear-7.5 cm-good coincidence with Alexx calculations.
akojic
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Post by akojic »

It seems that accumulator spere on my Xantia is not in good condition any more, although it has been replaced six months ago. Clicking period varies from 4 or 5 seconds up to 25 seconds. When applying brakes, clicks every couple seconds. I contacted service (where all 5 spheres were fitted last November) and it seems that they would replace it without charging too much. I was suspecting that empty (false) accumulator sphere might affect currently not consistant braking and fast sinking after tutning off the engine (especially back of the car after 20 min.) Any comments that would confirm my thoughts?
Car is 1.8i from 1993, just ordinary hydropneumatic system consisted of 5 spheres.
One more doubt - is brake valve = brake cylindres? It seems that some mechanics do not have any clue what brake valves are and where they might be found on car such is mine!
Thanks in advance for answers.
mark_l
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Post by mark_l »

May I add Excell file to my message? If positive-how?
(I make simple table for spheres actual pressure calculations, based on Alex formulas.)[:)]
Regards
blueboy2001
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Post by blueboy2001 »

Akojic - Sounds like your Xantia is behaving in exactly the same way as mine - very regular clicking in spite of a new accumilator that has been tested. My brake pedal is known to pulse a bit sometimes, seems to be in time with the pump action.
This, combined with rapid sinking at the back lead me to think the brake valve had had it. I therefore spent one Sunday with the assistance of Neil, the workshop foreman from work and changed it. If the thought has ever crossed anyones mind, don't even try it! It took us 3 1/2 hours to remove the old one, not before removing all the induction hosing, rocker cover, couple of diesel hoses and the inlet manifold to gain access. Neither of us had any skin left on our knuckles when we'd finished, then we discovered the return hose was perished and decided not to put anything back till we'd sourced a replacement. 3 days later, £150 lighter the car was back on the road. Fired her up with great anticipation, only to be met with tick, tick tick!! To say I wasn't impressed is a bit of an understatement.
I now believe the regulator itself is knackered. The bloke who did my spheres had a mess with it tapping a drift inside and it did give me about 3 days of a 50 second tick interval, but soon returned to normal. He said the springs in them go slack causing it to operate too often. I'm going to take it in to Pleides to get it fixed as I still use the Xantia a fair bit for my contracting business.
alexx
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Post by alexx »

Well, I was coping with similar problem 6 years ago, when I bought my BX. It turned out that brake valve was the main problem, but also, I tested the regulator.
Unfortunately, I couldn't find a garage equipped with a simple pressure-meter (they said they didn't need it), so I tested the regulator without it, this way:
- disconnect brake-valve return pipe from LHM tank and push it into a bottle (1-2 l)
- put the suspension into the lowest position (to cut off suspension part of the system)
- switch the engine on
- wait a minute or two
- keep applying and releasing brakes (as quick as possible) until the bottle is full, and count the regulator ticks (have an assistant)
- divide the bottle volume with the number of ticks
With new accumulator sphere, you should theoretically have 18.3 ml of LHM per one tick. If this number is significantly lower, and the sphere is on correct pressure, than the difference between cut-in and cut-off pressure in the regulator is too low.
I got about 12 ml per one tick, so there are 3 possibilities:
1. the pressure in newly regassed sphere was 40 instead of 62 bar, because of not-very-precise pressure meter in the garage where I regassed the sphere
2. the difference between cut-in and cut-off pressure in the regulator was only 16 bar instead of 25
3. combination of 1. and 2. (most likely).
akojic
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Post by akojic »

Ok Alexx, thanks for reply also thanks to blueboy2001. My simple question is: where is brake valve situated (I can not explain mechanic in Croatia who should have known this - works in Cit. garage)? Is it part of the high corrector, or is it situated elswere, as totally independent part of hyd.system? Does doseur valve might have influence on explained problem of my Xantia and what is the purpose of this valve?
Thanks
alexx
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Post by alexx »

On BX, brake pedal is acting directly onto brake valve. On Xantia, the arangementi is similar, but there's a kind of spring in between. It's under the LHM tank on Xantia (LHD models), there are 4 metal pipes and 2 rubber return pipes connnected. Mechanics here usually call it 'main brake cylinder', but it's in fact a valve (there are 3 slide valves and 4 springs inside).
Fast sinking of rear end is usually connected with worn brake valve, but the problem may be elsewhere (suspension cylinders, height corrector). Fast ticking of regulator can be also connected with worn brake valve, like in my case, but the problem can also be leakage in some other element or the difference between cut-in and cut-off pressure in regulator being to low.
Try fully depressing the brake pedal with the engine on. If you notice that the time between ticks is much longer, it's verly likely that the brake valve is worn (this 'test' worked in my case and on friend's XM).
jeremy
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x 2

Post by jeremy »

There are 2 other ways for high pressure LHM to escape from the accumulator, one is along the piston which is unlikely unless the regulator is severely worn and the other (very likely in my experience) is back the way it came in - ie past the non-return valve when the supply pressure drops.
This valve is a ball bearing valve and can be re-seated by tapping it smartly once with a BRASS rod.
jeremy
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